1. Field of the Invention
This invention relates to a sewing machine, and more particularly to a drive device provided for the sewing machine which is adapted to drive a main shaft and other mechanisms subjected to transmission from the main shaft.
2. Description of the Related Art
A clutch motor as shown in FIG. 1 have been known as a sewing machine motor in the art. The clutch motor is constructed as follows: A flywheel 2 is fixedly mounted on an output shaft 1a of a motor body 1, which is continuously rotated. A clutch plate 5 is rotatably supported by a movable bearing 4, which is axially, movably supported by a motor frame 3. A lever 7 provided to move the movable bearing 4 axially is urged by a lever return spring 8 so that the clutch plate 5 is pushed against a brake shoe 6. When the lever 7 is at rest, the clutch 5 is maintained pushed against the brake shoe 6, and therefore a sewing machine pulley 10 is held stopped. By pushing down the lever 7, the clutch wheel 5 is brought into contact with the flywheel 2, so that the sewing machine pulley 10 is turned.
The drive device for the sewing machine of this type is designed so that the main shaft is rotated at a low speed because it is locked to a one-way clutch upon rotation of a pulley adapted for power transmission to a low speed auxiliary motor as rotated when the main motor is in a neutral position. In this condition, the clutch plate 5 is out of contact with the flywheel 2 and the brake shoe 6, as shown in FIG. 1. The main shaft is rotated at a high speed in the same direction simultaneously with idling the pulley upon rotation of the main motor when the auxiliary motor stops. A disadvantage derived from the conventional drive device is that a transmission mechanism is complex and costly when a mechanism is used wherein the aforementioned clutch motor is employed for low speed controls such as needle position control and thread cutting or trimming.